The combination of laboratory and numerical experiments is a powerful tool to study rock physical processes. While in laboratory experiments it is very difficult (or impossible) to control all the physical processes, in numerical experiments they can be controlled exactly. Numerically, it is even possible to study different physical processes separately from each other, which otherwise coexist in nature. Here, our objective is to understand the fluid-related physical process responsible for intrinsic attenuation in saturated rocks at seismic frequencies. For that, we measured in the laboratory local transient fluid pressure along a partially saturated rock sample. Furthermore, we compared the laboratory results with values calculated numerically using a 3D poroelastic numerical model to approximate the partially saturated rock sample.

Estimating pore fluid properties of partially saturated porous rocks from seismic data is very important in exploration geophysics for finding economically viable hydrocarbon reservoirs and in reservoir geophysics for monitoring and optimizing production. Field data, as well as theoretical and experimental studies, show that pore fluid properties have a major effect on attenuation and velocity dispersion of seismic waves. To better understand this effect, we compare laboratory measurements and numerical computations of attenuation in the frequency range between 0.1 and 100 Hz. While in laboratory experiments all possible physical mechanisms for attenuation occur simultaneously, with numerical modeling we separately study the effects of a single physical mechanism: wave-induced fluid flow in the mesoscopic scale. We show that this mechanism can explain the attenuation measured in the laboratory experiments for the fluid-saturated sample if the anelasticity of the solid frame is taken into account.